<?php
$username = '李四';
?>

<html>
    <head>
        <style>
            div{
                background-color: red;
                color: #ffffff;
                width: 200px;
                margin: 0 auto;
                text-align: center;
                height: 500px;
                line-height: 500px;
            }
        </style>
    </head>
    <body>
        <div>欢迎您，<?php echo $username;?></div>
    </body>
    <script>
        alert('Hello World')
    </script>
</html>